Answer: Pelagic zone
Step-by-step explanation:
The upper most zone of ocean has highest number of producers. This zone receives highest amount of sunlight.
Sunlight is the required for the process known as photosynthesis which is used to make food by the help of other important components.
These organism are plankton that helps in the production of carbohydrate and oxygen.
So, the correct answer is epipelagic zone.